High-capacity electric storage devices are employed as a power source for various equipment such as hybrid electric vehicles (HEV), electric vehicles (EV), electric motorcycles, aircrafts, and ships. Such an electric storage device is provided with a rechargeable electric storage element, such as batteries (lithium ion batteries, nickel hydrogen batteries, or the like) and capacitors (electrical double-layer capacitors, or the like), and a bus bar that is electrically connected to the electric storage element.
The electric storage element is provided with an electrode assembly that includes a positive electrode plate and a negative electrode plate, a case that houses the electrode assembly, and an external terminal that is electrically connected to the electrode assembly and arranged outside the case. The number of the electric storage element to be provided is at least one. That is, the number of the electric storage element to be provided in an electric storage device corresponds to the output (capacity) of the electric storage device.
The bus bar serves to connect electric storage elements electrically to each other, or to connect each electric storage element electrically to an external load. Therefore, the bus bar is composed of a metal material having electrical conductivity, and has a connection region that is connected to the external terminal of the electric storage element. The bus bar (connection region) is connected to the external terminal of the electric storage element by screwing or welding. This allows the bus bar to be connected to the external terminal not only electrically but also mechanically. In the electric storage device of this type, the charge or discharge state, the service life, or the like, of the electric storage element is monitored by a monitoring device mounted on the electric storage device or a monitoring device configured as a separate body from the electric storage device. Following this, a wiring member that transmits information (signals of voltage, temperature, etc.) on the electric storage element between the electric storage element and the monitoring device is connected to the bus bar. That is, the bus bar is provided with a receiving portion to which a screw member for connecting the wiring member or a conductor such as a rivet is secured.
When the bus bar is connected to the external terminal of the electric storage element, the bus bar is required to be positioned relative to the external terminal of the electric storage element so that the relative arrangement between the bus bar and the external terminal should be appropriate. Following this, there is proposed a method in which an electric storage element is provided with a projection, and a bus bar is provided with a receiving portion so that the receiving portion of the bus bar and the projection of the electric storage element are fitted together, thereby positioning the bus bar relative to the electric storage element (see, for example, JP 2011-71104 A).
However, the above-mentioned method may require work to adjust the arrangement of the electric storage element in the manufacture of the electric storage device in some cases. In the worst case, the electric storage element and the bus bar may fail to be appropriately connected to each other.
This problem is more specifically described below. In the conventional method, based on the premise that the relative arrangement between the bus bar (connection region) and the electric storage element (external terminal) is maintained always constant, the receiving portion of the bus bar is provided adjacent to the connection region and the projection of the electric storage element is provided adjacent to the external terminal. Therefore, if the electric storage element is mispositioned, or the arrangement of the receiving portion is displaced from a predetermined position due to poor machining accuracy, the positional relationship between the external terminal and the receiving portion may fail to be consistent with the positional relationship between the external terminal and the projection in some cases. That is, even if the bus bar (connection region) is arranged so as to be connectable to the external terminal, there may be some cases where the bus bar cannot be positioned relative to the external terminal because of failure to insert the projection into the receiving portion.
Therefore, the conventional production method sometimes requires not only adjusting the arrangement of the bus bar but also appropriately adjusting the arrangement of the electric storage element when arranging the bus bar. Further, the electric storage element may sometimes be supplied in a state of being already positioned at a given position. In such a case, the arrangement of the electric storage element cannot be adjusted to the arrangement of the bus bar, as a result of which the bus bar may fail to be connected appropriately to the external terminal of the electric storage element.